1. Field of the Invention
The present invention relates to an IC card for receiving external energy and transmitting and receiving data to and from an external unit with no contact between them, and particularly to an IC card which can prevent erroneous operations in receiving energy and transmitting and receiving data.
2. Description of the Prior Art
FIG. 1 is a view generally showing functions of a light communication system using an IC card.
The light communication system comprises an IC card 101 and a data read/write unit 111 for reading and writing data from and to the IC card 101 inserted into the unit 111. The data read/write unit 111 is connected to a host computer 121 through data lines 112. When the IC card 101 is placed in the data read/write unit 111, data are read out of and written into the IC card 101 by the data read/write unit 111 with light energy with no contact between the IC card 101 and the unit 111.
The data read/write unit 111 comprises a data manipulating portion 113 for storing, processing, writing and reading data, connected to the host computer 121 through the data lines 112; a power supplying portion 114; a light emitting element 116 for transmitting data; and a light receiving element 117 for receiving data. The power supplying portion 114 and the elements 116 and 117 are separately connected to the data manipulating portion 113. The power supplying portion 114 is connected to an ultraviolet lamp 115 which is a light energy radiator facing a solar battery element 102 which is a power generating and supplying element of the IC card 101. When the IC card 101 is inserted into the data read/write unit 111, the light emitting element 116 of the unit 111 faces a light receiving element 103 which is a data receiving element of the IC card 101, and the light receiving element 117 of the unit 111 facing a light emitting element 104 which is a data transmitting element of the IC card 101.
The solar battery element 102 of the IC card 101 generates power when receiving light energy from the ultraviolet lamp 115 of the data read/write unit 111 to drive the IC card 101. The light receiving element 103 of the IC card 101 receives data from the light emitting element 116 of the unit 111, while the light emitting element 104 of the IC card 101 transmits data to the light receiving element 117 of the unit 111. For the light emitting elements and light receiving elements, there are used light emitting diodes and light receiving diodes. The host computer 121 stores information to be communicated. If the amount of information is not so large, the function of the host computer 121 may be carried out by the data manipulating portion 113.
FIG. 3 is a cross-sectional view showing the IC card 101 of the prior art. The power generating element 102, the light receiving element 103 and the light emitting element 104 are disposed on one main surface (a front surface) 118 of the IC card 101 to face the ultraviolet lamp 115, the light emitting element 116 and the light receiving element 117 of the data read/write unit 111. These elements 102, 103 and 104 of the IC card 101 are electrically connected to a data manipulating element (an IC) 105 for storing, processing, writing and reading data, incorporated in the IC card 101.
FIG. 2 is a cross-sectional view showing the IC card light communication system with the IC card 101 being inserted. Under this condition, the power generating element 102, the light receiving element 103 and the light emitting element 104 arranged side by side on the one main surface 118 of the IC card 101 face the ultraviolet lamp 115, the light emitting element 116 and the light receiving element 117 of the data read/write unit 111, respectively.
Meanwhile, to drive an IC card and an external data read/write unit for reading and writing data from and to the IC card with no contact between them, there have been proposed various systems such as a system using radio waves and a system using light as mentioned in the above. The system using radio waves requires complicated circuits for transmitting and receiving data that is disadvantageous to the IC card which shall be small and lightweight. On the other hand, the method using light can be materialized with semiconductors which are inexpensive and with semiconductor pellets themselves to reduce the size and weight of the system. Therefore, IC cards using light are widely used.
To drive the IC card and the data read/write unit with no contact between them, two kinds of semiconductor elements are indispensable, one for supplying power and one for data communications. According to the IC card light communication system of the prior art mentioned in the above, two kinds of the semiconductor elements each having different function are disposed side by side on one main surface of the IC card such that part of the semiconductor elements is exposed. Since signals given for the semiconductor elements are of light energy for both the functions of the elements, the signals may interfere with each other to cause the elements to receive erroneous signals, thereby causing an erroneous operation of the IC card and seriously deteriorating reliability of the system as a whole. In addition, some of the semiconductor photoelements require special filters to be coated over the surfaces thereof to prevent this effect of light energy.